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 Post subject: Minimal build `386 transmitter
PostPosted: Dec Sat 09, 2017 3:21 am 
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Powered by a 12VDC wallwort, this LM386 module only needs the last capacitor changed to an inductor (red) to feed the oscillator then to the "loopstick, paralleled by a small cap. Not much "building" required. I had several slug tuned coils. A small var cap and coil would work even better?

Image

With the new little no frills MP3 player.

Image

Was holding off for a "finished box"... but I keep seeing questions about where to buy transmitters.
There is no excuse for not trying to build something. I find the hardest part is waiting for parts from China and keeping the interest for 2+ weeks.


Another slug Tooned 6888 transmitter...
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 Post subject: Re: Minimal build `386 transmitter
PostPosted: Dec Sat 09, 2017 5:20 am 
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That looks easy enough...

I like your orange tuning knob, fixed a lamp(removed touch module) yesterday for wife, used a pair...


I'd post schematic for my 9KC6 xmitt, but compared to a 6888 it's a bit complex... Once I got the bugs worked out it's my favorite but no one is gonna build it, I likely have the only one in existence...


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 Post subject: Re: Minimal build `386 transmitter
PostPosted: Dec Sat 09, 2017 7:45 am 
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Hey Mike, nice touch using a wire nut for a tuning knob, lol!

So can you make a schematic of this little beauty, or at least define the change to the Chinese amp module, that is what kind of inductor (also it looks like C6 was replaced with a resistor), and the added coil and crystal circuit?

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 Post subject: Re: Minimal build `386 transmitter
PostPosted: Dec Sat 09, 2017 10:38 pm 
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I love this!


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 Post subject: Re: Minimal build `386 transmitter
PostPosted: Dec Mon 11, 2017 3:08 am 
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Very nice.

A quite simple way to build the transmitter.

Quite possibly cheaper than buying the parts to build the LM-386 circuit.

Would be nice to see a kit sold with the parts.

Perhaps could be made in such a way to where the amp module and TCXO just plug in if it would be legal to be sold like that.

I've often thought of using the LM-386 transmitter with a raspberry pi so I could have an all in one music source, processor and transmitter.


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 Post subject: Re: Minimal build `386 transmitter
PostPosted: Dec Fri 22, 2017 4:58 am 
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Update with enclosure.

The mini MP3 player is 5-12V and accepts the Chinese remotes, (but not included) It has volume, FF and 5 equalizer settings, but only accessible by remote. $2.58 shipped. https://www.ebay.com/itm/5V-7-12V-Mini- ... 2749.l2649

This transmitter works very well and with a 15' wire ceiling antenna and a ground covers a couple houses directionally.
I must mention my ground is several 5' copper pipes in the ground AND my two 30' CB antenna masts are also grounded to the pipes. No doubt helping.

Using a 12V wallwort the ground isn't needed, but helps.
Image

Been playing for a couple hours on 9V.


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 Post subject: Re: Minimal build `386 transmitter
PostPosted: Jan Tue 02, 2018 4:56 am 
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Very nice Mike. Any chance of a schematic, and details of the mod?


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 Post subject: Re: Minimal build `386 transmitter
PostPosted: Jan Tue 02, 2018 4:59 am 
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[quote="35Z5"

I'd post schematic for my 9KC6 xmitt, but compared to a 6888 it's a bit complex... Once I got the bugs worked out it's my favorite but no one is gonna build it, I likely have the only one in existence...[/quote]
You never know, someone might just be brave enough to build its twin!


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 Post subject: Re: Minimal build `386 transmitter
PostPosted: Jan Tue 02, 2018 3:37 pm 
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Nice project! Would love to build the 386 xmitter myself.

Schematic?


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 Post subject: Re: Minimal build `386 transmitter
PostPosted: Jan Tue 02, 2018 3:58 pm 
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Colin Ames wrote:
35Z5 wrote:

I'd post schematic for my 9KC6 xmitt, but compared to a 6888 it's a bit complex... Once I got the bugs worked out it's my favorite but no one is gonna build it, I likely have the only one in existence...

You never know, someone might just be brave enough to build its twin!

OK, once I get the schematic cleaned up from probably a half dozen revisions, I'll start a new thread...

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 Post subject: Re: Minimal build `386 transmitter
PostPosted: Jan Tue 02, 2018 4:59 pm 
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Do you have a source for the inductor? Been looking for one with the screw adjustment. Mine need a hex tuning tool inserted and are not very easy to fine tune.

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 Post subject: Re: Minimal build `386 transmitter
PostPosted: Jan Tue 02, 2018 8:44 pm 
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I had bought several loopsticks (no numbers) on ebay years ago. I just experimented with the loopstick and caps on a crystal set to get around 1,000kc.

Image

Image


Last edited by Mike Toon on Jan Tue 02, 2018 8:56 pm, edited 1 time in total.

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 Post subject: Re: Minimal build `386 transmitter
PostPosted: Jan Tue 02, 2018 8:52 pm 
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Thanks Mike!


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 Post subject: Re: Minimal build `386 transmitter
PostPosted: Jan Tue 02, 2018 9:41 pm 
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Yes, thanks Mike. Good information. 8)

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 Post subject: Re: Minimal build `386 transmitter
PostPosted: Jan Tue 02, 2018 10:48 pm 
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Thanks Mike!


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 Post subject: Re: Minimal build `386 transmitter
PostPosted: Jan Tue 02, 2018 11:04 pm 
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fifties wrote:
... or at least define the change to the Chinese amp module, that is what kind of inductor (also it looks like C6 was replaced with a resistor), and the added coil and crystal circuit?


The resistor looking thing (C6) is the inductor. All Electronics has them, 3/buck. https://www.allelectronics.com/item/cc- ... oil/1.html


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 Post subject: Re: Minimal build `386 transmitter
PostPosted: Jan Sat 06, 2018 1:00 am 
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Well I am a believer now. Got my oscillators from DigiKey today. Took about 20 minutes to hook up the parts on the breadboard. I am not using the LED so I set the power supply at exactly 9 volts. I went with an adjustable inductor and eliminated the variable capacitor. I tuned with an RF probe loosely coupled to the variable inductor. Antenna tunes perfectly. Audio is great and signal is really strong over my entire house. Not using the Mp3 module since I stream Pandora through an old iPhone. Really hard to believe it can be this simple!

Now I need to find something cool to house it in.

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 Post subject: Re: Minimal build `386 transmitter
PostPosted: Jan Sat 06, 2018 5:21 pm 
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black85vette wrote:
Well I am a believer now.

Audio is great and signal is really strong over my entire house.

Really hard to believe it can be this simple!


Ain't it a bitch?? I mostly run my tube unit(s), still I'm impressed every time I turn on my "386"...

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 Post subject: Re: Minimal build `386 transmitter
PostPosted: Jan Sat 06, 2018 10:36 pm 
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Yeah I like my 2 tube transmitter. Just something about an orange glow and warmth of the tubes.

BTW; I had one of these in my collection of "stuff":

https://www.amazon.com/gp/product/B01GJ0SC2C/ref=oh_aui_detailpage_o02_s00?ie=UTF8&psc=1

Input: DC 3 V to 40 V (input voltage must be 1.5 V higher than the output voltage, no boost)
Output: DC 1.5 V to 35 V voltage is continuously adjustable, maximum output current is 3 A

I find them useful when I need a variable voltage supply that I can incorporate into a project. Small and cheap. Not as cheap as an LM317 but very convenient. Powering it with a 12 volt Astron linear supply. Overkill but hum and noise free. Now this transmitter can go portable with a 12v battery.

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 Post subject: Re: Minimal build `386 transmitter
PostPosted: Jan Sun 07, 2018 12:35 am 
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I was looking at something like that, I saw someone else had a schematic for a modulated xtal osc, too, on a google search. But someone else told me that the can oscs maybe do not accept modulation of the DC input very well or at all? Maybe some others have a regulator or something in them that blocks the audio? My pipedream was to make use of an old mono FM tuner and BC AM out to vintage radios with it. Instead of having two boxes setting around, a tuner and a seperate AM trans. Install the small AM board in the tuner and take power from tuner. Not much demand for mono FM tuners or at least cheap ones. I got one for 5 bucks.


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